The present invention concerns a measurement arrangement for measuring and/or monitoring a physical property, comprising: a measurement device comprising: at least one primary sensing element to be exposed to a product at a measurement site, mounting means for mounting said primary sensing elements at said measurement sites, a secondary measuring device, mounting means for mounting said secondary measurement device, and transmission lines connecting each primary sensing element to said secondary measurement device.
Measurement devices for measuring and/or monitoring physical properties form the bases of modern process automation and are widely used in nearly all fields of industry for measuring, monitoring and/or controlling process parameters.
There is a large number of applications, where rough conditions prevail at the measurement site. This is for example the case, when the measurement site is exposed to high temperatures, or when physical properties of highly corrosive or abrasive process media are to be measured. Since not all components of the measurement device are able to withstand these conditions, measurement devices are used comprising primary sensing elements, which are mounted directly at the measurement sites, and are connected to a remotely located secondary measurement device via transmission lines. Thus the secondary measurement device can now comprises all those components of the measurement device, which are unable to withstand the conditions prevailing at the measurement site.
One example for corresponding measurement arrangements are pressure measurement arrangements comprising diaphragm seals as primary sensing elements. Diaphragm seals comprise a membrane to be exposed to the pressure at the measurement site, and are connected to a remotely located secondary pressure measurement device, e.g. a pressure transmitter comprising a sensor and corresponding measurement electronics, via capillary tubes. Diaphragm seals are not only used in harsh environments, but also in applications wherein good and rapid cleaning of the measurement site is required.
Other examples are applications wherein the primary sensing elements are sensors, detectors, antennas, transducers or probes, which are connected to secondary measuring devices comprising for example sensitive measurement electronics, via purely electric transmission lines, like for example uni- or bidirectional signal transmission lines or power supply lines.
The transmission lines normally comprise an inner core, e.g. an inner pressure transmitting capillary, or one or more cables or lines, and an outer tubular protection conduit enclosing said core, and are directly connected to the primary sensing elements.
When the primary sensing elements are used in applications, where they are subjected to strong vibrations at the measurement site, this vibration will affect the end section of the transmission line connected to the primary sensing element. At the same time, the other end of the transmission line connected to the secondary measuring device will remain essentially motionless due to the remote location of the secondary measuring device. In the long run, the resulting strain on the transmission line may cause the core therein and sometimes also its tubular protection conduit to break close to the primary sensing element.
It is an object of the invention to provide a measurement arrangement comprising at least one primary sensing element, a remotely located secondary measurement device, and transmission lines connecting each primary sensing element to the secondary measuring device, for applications wherein the primary sensing elements may be exposed to strong vibrations at the measurement sites.
To this extend the invention comprises a measurement arrangement for measuring and/or monitoring a physical property, comprising a measurement device comprising:                at least one primary sensing element to be exposed to a product at a measurement site,        mounting means for mounting said primary sensing elements at said measurement sites,        a secondary measuring device,        mounting means for mounting said secondary measurement device above said measurement sites,        transmission lines connecting each primary sensing element to said secondary measurement device, said transmission lines comprising:                    an inner core,            an outer tubular protection conduit enclosing said core, and            a vibration absorbing medium filling an interior of said outer protection conduit surrounding said inner core.                        
According to a preferred embodiment, the vibration absorbing medium is a powder, in particular an aluminum oxide powder, a liquid, or a gel, in particular a silica gel.
The invention further comprises a measurement arrangement according to the invention, comprising a single primary measurement element, wherein                said physical property is a pressure of a product at a single measurement site,        said primary sensing element is a diaphragm seal,                    said diaphragm seal comprising a membrane to be exposed to said pressure at said measurement site,                        said secondary measuring device is a pressure measurement device, and        said transmission line is a capillary tube,        said inner core is a capillary inside said capillary tube, and        a pressure transferring liquid is foreseen, filling an inside of said diaphragm seal and said capillary for transferring said pressure onto said pressure measuring device.        
The invention further comprises a measurement arrangement according to the invention, comprising a first and a second primary measurement element, wherein                said physical property is a differential pressure between a first pressure at a first measurement site and a second pressure at a second measurement site,        said first primary sensing element is a first diaphragm seal comprising a membrane to be exposed to said first pressure at said first measurement site,        said second primary sensing element is a second diaphragm seal comprising a membrane to be exposed to said second pressure at said second measurement site,        said secondary measuring device is a differential pressure measurement device,        said transmission lines are capillary tubes,        said inner cores are capillaries inside said capillary tubes, and        a pressure transferring liquid is foreseen, filling an inside of said first and said second diaphragm seal and said capillaries for transferring said first and said second pressure onto said differential pressure measuring device.        
The invention further comprises a measurement arrangement according to the invention, wherein:                said primary sensing element comprises a sensor, a detector, an antenna, a transducer, or a probe,        said secondary measuring device comprises a measurement electronics, and        said inner core of said transmission line comprises at least one cable or line for electrically connecting said primary sensing element to said secondary measurement device.        
According to a refinement of said last mentioned arrangement said primary sensing element comprises an extension enclosing an electric connector for electrically connecting said primary sensing element to at least one cable or line of said core of said transmission line.
According to a further refinement, an end of said outer conduit is equipped with a sleeve nut, which is screwed onto an outer thread of said tubular extension.
According to further embodiments of said last mentioned arrangement, said measurement device is a level measurement device for measuring a level of a product in a container, in particular a time of flight microwave level measurement device comprising an antenna, a guided radar time of flight level measurement device comprising a conductive probe, a capacitance level measurement device comprising a capacitance probe, or an ultrasonic level measurement device comprising an ultrasonic transducer.
According to another embodiment of said last mentioned arrangement, said measurement device is a level switch for monitoring a predetermined level of said product in a container, and said primary sensing element comprises a mechanically oscillating structure extending into said container at a height corresponding to said level to be monitored, and an electromechanical transducer for causing said structure to oscillate and for transforming a resulting oscillation of said structure into an electric measurement signal.
The invention and its advantages are explained in more detail using the figures of the drawing, in which seven exemplary embodiments are shown. The same reference numerals refer to the same elements throughout the figures.